It is known to provide a 100BASE-FX PMD/PMA/PCS transceiver which plugs into a hub or switch to provide 100BASE-FX connectivity. The device uses a proprietary interface based on the IEEE802.3 MII interface. This method requires a MAC or repeater port to be provided on the system plus a connector. The parts required to perform these functions must be provided whether or not the optional transceiver is fitted.
The aim of this invention is to minimise the cost overhead carried by the host system when providing support for 100BASE-FX connectivity.
The invention is to provide an interface between the system and the optional module at the PMD/PMA interface. In prior systems this interface has been provided at the MII interface. The invention only requires comparatively few connections for the interface, so reducing the cost of the connector required. This also means the PHY device is part of the main system which ensures all management functions can be used. As suitable PHY devices generally also provide 10BaseT and 100BASE-TX support the PHY device can be used to provide 10/100 TX connectivity when not required for the 100BASE-FX module. This therefore means that in order to provide 100BASE-FX connectivity to a switch or hub it is simply necessary to switch the PHY for one of its 10/100 ports from 10/100 TX operation to 100BASE-FX operation and attach the PMD device (Fibre transceiver). This provides a considerable cost saving, in a multiport hub or switch when compared with the provision of a dedicated port and MII connector.
In one aspect of the invention, a fibre optic transceiver is intended to be external to the device and is not only connected to a standard plug for the twisted pair connector but is also connected by way, for example, of a driver to signal detect inputs for the male plug. In another aspect of the invention the corresponding signals from the connector are coupled by way of an isolating coupling, such as opto electric coupler, to a logic circuit which will switch the physical device from the `twisted pair` (MLT3) mode to the `fibre optic` (NRZI) mode if the fibre optic coupler is present and a signal is detected thereon.